Food scientists argue that near-infrared spectroscopy would work better than other methods to detect food fraud.

“The problem is that the food analyses which are predominantly used today are only spot checks and they are typically targeted towards a single kind of food fraud,” says coauthor Søren Balling Engelsen, a professor in the food science department at the University of Copenhagen. “We would like to move away with this old-school methodology and instead take a “non-targeted” physicochemical fingerprint of the foodstuffs.”

“By using fingerprints and contrasts we can determine whether a given batch of raw materials or ingredients are defective or different compared to the usual,” he says.

Near-infrared spectroscopy can provide a physicochemical fingerprint of a biological sample by sending light into a substance and measuring the light that comes back. The fingerprint will often contain over 1,000 spectral variables that each relate to the physicochemical composition of the food in their own unique way.

The “fingerprint,” or spectrum, can be compared to a validated fingerprint of the same sample material with the use of multivariate data analysis, called chemometrics. The measurement will detect fluctuations in many different ingredients at once, which is why it is a “non-targeted” method of analysis.

Melamine in baby formula

The article, published in Current Opinion in Food Science, mentions a case from 2008, in which Chinese manufacturers added melamine to milk powder for infant formula, causing 300,000 children to fall ill and 6 to die.

Melamine, a synthetic substance with 66 percent nitrogen, was added to the milk powder to make customers believe that it contained more protein than was actually the case and thus had a higher value. The fraud succeeded tragically, because “protein content” was checked using the old Kjeldahl method—a type of analysis that measures the total nitrogen content in the food, which is then equated with the protein content. In this case, the detected substance was not protein, but the hazardous melamine nitrogen.

“Now there is probably no longer anyone who would think about putting melamine in milk powder. An alternative nitrogen-rich substance could be urea, or in popular terms “piss in the powder,” where nitrogen-rich urea is used to fool the Kjeldahl analysis—but not NIR spectroscopy,” says Engelsen.

Gum arabic manipulation

Another advantage of NIR spectroscopy is that you can examine large quantities of raw materials or ingredients. With spectroscopic monitoring it is possible to examine close to 100 percent of the ingredients and raw materials that go into the production, thereby considerably reducing production errors or productions that are of a lower quality than the recipe dictates. At the same time, the company can use the method to optimize its use of raw materials and to achieve a consistent, environmentally safe production.

A good example of a food ingredient that can be manipulated by the suppliers is the desirable gum arabic (E414), which has some valuable properties as a stabilizer and for chewing properties and flavor release.

“However, it is easy to adulterate food with gum arabic, when it appears in the form of freeze-dried powder, which many suppliers have gradually started to sell. Previously, it was found most often in the form of “tears” from the acacia tree—that is, as large amber-like clumps that cannot be easily forged. But it has been difficult to obtain high quality gum arabic because of the war and unrest in the growing areas (South Sudan).

“As a powder, it is easy to falsify the gum arabic by mixing an inferior quality with the good and sell it all as being of a high quality. This kind of fraud can also be detected by NIR spectroscopy,” says Engelsen.

A shift in methods

“We have known and developed these methods for 20 years and they have become better and cheaper over time. The use of NIR spectroscopy to monitor food quality was already endorsed in the 1970s when Canada began to replace the chemical requiring and cumbersome Kjeldahl analysis with NIR spectroscopy to analyze their cereals for the protein content. For this purpose, NIR spectroscopy is exclusively used as a targeted method i.e. for measuring protein content.

“But when you want to detect food fraud and food adulteration, you are not looking for a single substance, but have to look broadly. An increased use of NIR spectroscopy will definitely be able to save us from many forms of food modification that could be of more or less serious kinds—from receiving lower quality products to becoming seriously ill,” says Engelsen.